1. Field of the Invention
The present invention relates to an antenna, more specifically relates to an antenna suitable in hand-held device.
2. Description of Related Art
Development of a variety of high-tech electronic products is to facilitate people's lives, including a variety of electronic devices, such as notebook computers, mobile phones, personal digital assistants and so on. With the popularity and the increment or people's desires for high-tech electronic products, the configuration of the functions and applications of these high-tech electronic products are substantially increasing, especially the wireless communication function is widespread for the people's mobile devices. Thus, people can use these high-tech electronic products with wireless communication function in any location and at any time to get benefit of using flexible and convenient high-tech products. In view of the foregoing advantages, the location will not be the limitation for people to use the electronic products no longer, and the applications of these electronic products truly facilitate people's lives.
Since the applications of these electronic products increase, people have wider requirements to various applications, especially using these electronic products in a variety of frequency bandwidth. So that, dual-band or tri-band antenna structure usually sets up in these electronic products to be used to transceive and receive in a variety of frequency bandwidth. In order to have good transceiving and receiving signals in different environments, the antenna's structure and quality should be accurately designed.
Generally, a well-known antenna includes a dipole antenna, a monopole antenna, a patch antenna, a planar inverted-F antenna, a meander line antenna, an inverted-L antenna, a loop antenna, a spiral antenna, a spring antenna or the like. These antennas typically have larger size occupying larger space and increasing the size used in these electronic devices. However, these electronic devices are designed and developed to enable users easy to carry. Therefore, an approach to reduce the antenna size will be an issue for these electronic devices.
In addition, a conventional antenna has a second or third harmonic signal, or higher order harmonic signals. The high order harmonic signals will interfere with the transceiving and receiving signals, and will indirectly interfere with other wireless transmission devices and wireless communication devices. In the requirements of United States Federal Communications Commission (FCC), it sets the safety requirements for standard certification and provides intensity limitation to the high order harmonic signals of these antennas. For other countries, the same limitation in the safety requirements for standard certification is set. Due to the higher signal intensity of these high order harmonic signals, the electronic products using these antennas will not certified by the safety requirements for standard certification in the most countries. It causes these electronic products unable to be sold since they are not certified. Therefore, the approach to reduce these high order harmonic signals' intensity of the antenna becomes the problems to be overcome.